1. Technical Field
This invention is directed to a gel-like solid comprising polarizable particles dispersed in a lightly crosslinked polymer matrix.
2.Discussion of Relevant Art
It is generally known that electroviscous (EV) or electrotheological (ER) fluids exhibit pronounced reversible changes in apparent viscosity and resistance to shear in response to the application of an electric field. Such fluids generally comprise suspensions of finely divided, solid particles in an electrically non-conductive oil which can be rapidly and reversibly increased from the liquid to the plastic or solid state under the influence of a sufficiently powerful electric field. Both direct current electric fields and alternating current electric fields may be used for altering the viscosity. Such electroviscous fluids are proposed for use in shock absorbers and variable speed accessory drive clutches. Such fluids have the disadvantage, however, that the particles tend to settle and form separate phases in the fluid. The fluid nature of the ER fluids also precludes them from being used in applications such as for elastic (rubber) dampers with adjustable damping rate because they readily change their shape and flow upon the application of external forces. The ER fluids also require tight seals to prevent the fluid from leaking from their containers, e.g., an ER fluid type shock absorber.
It is an object of the present invention to provide a material which exhibits changes in its viscoelastic properties like shear modulus and loss factor (often referred to as damping factor) when subjected to an electric field. It is another object to provide such a material which is a gel-like solid so that the polarizable particles are maintained in a lightly crosslinked polymer matrix and not subject to settling. It is a further object of the invention to provide an electroviscous gel-like solid of sufficient rigidity which allows unique applications such as variable stiffness elastomers, vibration dampers, and accelerometers not available to ER fluids.